Soak dal in hot water for 20 minutes and pressure cook it keeping the mixed vegetables in a small container on it for 3 whistles. Soak tamarind in hot water and extract 1 1/2 cups of tamarind juice. Heat 1 tbsp of oil, add mustard seeds, when it splutters, add hing, red chillies, fenugreek seeds, curry leaves, finally chopped onions and saute for a few mins. Then add tamarind water, turmeric powder, salt as needed and BHARAT SAMBHAR MASALA. Let it boil until the raw smell of the tamarind and the masala goes. Approximately it will take around 10 minutes. Add the pressure-cooked vegetables to it. Then mash the dal well with a masher and add to the sambar along with needed water. Simmerand bring everything to a boil, until the sambar thickens a little. Garnish with coriander leaves and serve with steamed rice.